Hydraulic balance

ABSTRACT

A hydraulic balance is provided which comprises two deformable parallel tubes containing a fluid under pressure and arranged between a lower base plate and an upper load supporting plate, each of the tubes forming part of a separate hydraulic circuit having a separate pressure measuring device.

[15] 3,698,492 [45'] Oct. 17, 1972 United States Patent Lejeune 154]HYDRAULIC BALANCE [72] Inventor:

156] References Cited UNITED STATES PATENTS Daniel Lejeune, clermontFerrand, France 1,227,505 5/1917 Troll.... 2,095,268 10/1937 Roberts2,313,156 3/1943 Kratt,

sociale Michelin 8: Cie, Clermont-Ferrand,

France [73] Assignee: Compagnie Generale Des Etablissement MichelinRaison 1 Filed: y a 1971 Primary Examiner-Richard B; Wilkins [2] Appl.No.: 139,697 Assistant Examiner-George H. Miller, Jr.

Attorney-Brumbahgh, Graves, Donohue & Raymond Foreign ApplicationPriority Data 1 I [57] ABSTRACT A hydrauliebalance is provided whichcomprises two May 15, 1970 deformable parallel tubes containing a fluidunder [52] US. 177/203 [51] .G0lg 17/00, GOlg 5/04 pressure and arrangedbetween a lower base plate and Int. Cl.

an upper load supporting plate, each of the tubes Field ofSearch...............l77/126, 208, 209, 136

forming part of a separate hydraulic circuit having a separate pressuremeasuring device.

2 Claims, 3 Drawing Figures PATENTEDHBI 17 I972 INVENTOR.

DANIEL LEJEUNE HYDRAULIC BALANCE The present invention relates to ahydraulic balance designed to measure the load exerted on the earth by.each of the wheels of a vehicle, particularly heavy vehicles such asconstruction vehicles. v

It is frequently necessary to establish the'actual conditions of use ofconstruction vehicles and in particular the total weight'of the vehicleunder load as well as the distribution of this weight over its variouswheels. This is useful in particular in order to better adapt the tiresto the working conditions of the vehicles for which they are intended.

It is of course desirable to be able to measure the load borne by thetires on the very place of operation of the vehicle without having tobring it to a weighing station. However, there. is no weighing apparatuswhich is sufficiently strong, light, simple and accurate that it can Oneessential point of the invention is the-use of two tubes forming part ofseparate hydraulic circuits, that is to say, hydraulic circuits which donotcommunicate with each other. If two communicating tubes were used aspart of a single hydraulic circuit, the application of a load wouldresult in anidentical increase AP in both tubes. This increase inpressure AP woulddepend not only on the load but also on the distance ofthe load from the two tubes. In order to make a precise meabe easilytransported and installed on the construction site, can be used there tomeasure loads of several dozen tons and permits easy but reliablemeasurements.

The purpose of the invention is to fill this gap and to create a lightbut strong and accurate weighing apparatus.

The hydraulic" balance in accordance with the present invention ischaracterized by the fact that it comprises, arranged between a lowerplate forming the base and an upper plate forming the support for theload, two deformable parallel tubes containing a fluid under pressureand forming part of two separate hydraulic circuits, each provided witha pressure measuring device.

The principle of operation of the apparatus is as follows:

When the load to be measured is applied onto the upper plate which restson the two tubes, the pressure in the tubes and in the hydrauliccircuits of which they form a part increases, for instance by Al in oneof the tubes and AP in the other. Experience shows that the sum AF APprovided that certain precautions in operation are taken, is preciselyrelated to the load. Calibration then makes it possible to determine thevalue of the load from the sum of the measured increases in pressure AP,and AP The only condition which must be satisfied load act substantiallyuniformly and in any event symmetrically on the different portions ofeach tube in contact with the upper plate, without it being necessaryfor it to act equally on the two tubes. In practice, with the axes ofthe two tubes parallel, it is advisable that the point of application ofthe load be in the plane perpendicular to the axes of the two tubeswhich plane divides the portion of each tube in contact with the loadbearing plate into two practically equal portions; it is not necessaryfor this point of application to be equally spaced between the twotubes. When operating in this fashion, the precision may reach 1 to 2percent.

When it is desired to measure the load exerted on the earth by the wheelof a vehicle, it is relatively easy to see to it that the tire is on theupper plate of the balance in such a manner that its center plane isapproximately perpendicular to the axes of the tubes and equally spacedfrom the ends of each tube. On the other hand, it would be verydifficult to bring the axis of the wheel precisely at the midpointbetween the two tubes.

surement, it would be necessary for the load to be placed precisely atan equal distance between both tubes, which is difficult to doin'practice.

The invention will readily be understood by reference to theaccompanying drawings in which one embodiment is shown. In the drawings:

FIG. 1 shows in perspective a hydraulic balance in accordance with theinvention;

FlGS..2 and 3 show on a smaller scale the balance with one wheel locatedon the balance, seen parallel and perpendicular to the axes of the tubesand of the wheel, respectively.

k In the drawing, 10 is the lower plate of the balance which is intendedto rest on the ground. On this plate there are arranged two paralleltubes 11 and 12 within housings 13 and 14, respectively, formed ofchannel rests on the tubes 11 and .12 via two channel irons I7 is thatthe and 18, respectively, affixed to the upper plate 15.

Each tube 11 and 12 consists of a central portion 20 in contact with thetwo plates 10 and 15. This central portion is of rubber and has aninterior reinforcement, for instance of metal wires, enabling it towithstand a high pressure, for example or 200 bars.

These rubber tubes may, for instance, have an outside diameter of mm.and have a reinforcement made of two layers of steel cable. A tube ofthetype described in French Pat. No. l,489,l9l is excellently suitable.I

In addition to the central portion 20, each tube has on one end a cap 21and on the other end a cap 22 connected by a conduit 23 to a pressuregauge 24, a distributor 25 and a manual hydraulic pump 26.

The hydraulic pump makes it possible to establish an initial pressureof, for instance, 10 bars in each tube 11 or 12 by injecting into it asuitable fluid which is compatible with rubber, for instance water or amixture of water and soluble oil. This distributor 25 makes it possibleto place the tubes 11 and 12 alternately in communication with thehydraulic pump. In the normal operation of the balance, the twohydraulic circuits, each formed of a tube 11 or 12, its conduit 23 andits pressure gauge 24, are not in communication with each other.

FIGS. 2 and 3 show a wheel 32 of a vehicle mounted on the balance.'Ascan be noted from FIG. 3, the wheel 32 is arranged in such a manner thatit is substantially centered axially of the tubes 11 and 12, the centerplane M of the wheel tire being approximately equally distant from theside edges of the upper plate 15. For this purpose, centering marks 30and 31 are painted on said plate to facilitate guidance. On the otherhand, as shown in FIG. 2, it is not necessary for the wheel to beequally distant between the two tubes; this fact is very favorable sinceit is very difficult, if not impossible, precisely to center the wheelat equal distance between the two tubes. v

In order to effect a weighing, the pressure in each tube 11 or 12 isfirst of all brought by means of the pump 26 to an arbitrarily selectedinitial value of, for instance, bars. The vehicle is then advanced insuch a manner that the wheel whose load is to be measured is placed inthe position shown in FIGS. 2 and 3. The in creases in pressure AP, andAP are read from the two pressure gauges 24 and added together. Acalibration curve or table gives the corresponding weight as a functionof the sum of the increases in pressure.

When the weight or load is removed, the pressure drops back to a valueclose to and slightly less than the initial value as a result ofhysteresis. Before effecting a new measurement it is preferable that thepressure in the two circuits be brought to zero and then again to theinitial pressure of l0 bars.

The total weight of a hydraulic balance in accordance with the inventionwhich makes possible the measurement of loads of 50 tons and more isabout 100 kilograms distributed over several parts which can easily behandled. Of course, the invention is not limited to balances intendedfor the measurement of high loads; it

is possible to use them for measuring .loads of any value.

What is claimed is:

l. A hydraulic balance capable of accurately measuring the load on atire of a heavy vehicle comprising two deformable parallel tubesdefining a transverse symmetry plane and containing a liquid under equalpressure and arranged between a lower plate forming a base and an upperplate forming a support for the tire locatable along the transversesymmetry plane, each of said tubes forming part of a separate hydrauliccircuit having a separate pressure measuring device and having means fordistributing the liquid under equal pressure into each tube. v v

2. The method of accurately measuring the load on a tire of a vehiclewhich comprises locating the tire along the transverse symmetry planeatoptwo deformable parallel tubes containing a liquid under equalpressure, separately measuring the increase in pressure in each tube anddetermining the load from the sum of the increases in pressure.

1. A hydraulic balance capable of accurately measuring the load on atire of a heavy vehicle comprising two deformable parallel tubesdefining a transverse symmetry plane and containing a liquid under equalpressure and arranged between a lower plate forming a base and an upperplate forming a support for the tire locatable along the transversesymmetry plane, each of said tubes forming part of a separate hydrauliccircuit having a separate pressure measuring device and having means fordistributing the liquid under equal pressure into each tube.
 2. Themethod of accurately measuring the load on a tire of a vehicle whichcomprises locating the tire along the transverse symmetry plane atop twodeformable parallel tubes containing a liquid under equal pressure,separately measuring the increase in pressure in each tube anddetermining the load from the sum of the increases in pressure.